Alberg 30 Displacement and Weight Question Stress on Rigging/Mast

Discussion in 'Sailboats' started by wesley Sherman, Jan 30, 2020.

  1. wesley Sherman
    Joined: Jan 2020
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    Location: New York

    wesley Sherman Junior Member

    Let me preface this with I am a novice..
    I am restoring a Alberg 30, complete redo...eventually I will be blue water sailing again on this new to me boat. I am being very careful conscience of weight. Want I am wondering is when I eventually set sail, how much weight can I load this thing with before it will substantially start affecting speed and handling? how would I figure this out? Also at what point or would weight begin to put stresses on the standing rigging,? I know speed would be affected by weight, but is there a formula or guessula that would say 1 person = x lbs. Right now i know the engine will be 393 lbs with transmission and shaft. My weight is 235 lbs, Estimated fuel tank and 80 gallons is 619 lbs. 95 gallons of integrated water tanks 672 lbs. So just generally 1919 lbs or 1 ton. nothing else included. It was suggested to me by someone of unknown knowledge or intelligence that there boat drops 1" about every 800 ish lbs.
    Hull Type:
    Long Keel
    Rigging Type:
    Masthead Sloop
    LOA:
    30.27 ft / 9.23 m
    LWL:
    21.67 ft / 6.61 m
    Beam:
    8.75 ft / 2.67 m

    Draft (max):
    4.29 ft / 1.31 m
    Displacement:
    9,000 lb / 4,082 kg
    Ballast:
    3,300 lb / 1,497 kg

    So if at water line my boat weight is 9000 lbs. At what point is it over loaded other than when the sinks starts flooding the boat . Guess I am looking for how to balance the most i can carry for comfort and what will start affecting my speed and stressing the Rigging.
    Hope this makes sense

    Thank you in advance for any help you can give this psyc inmate!
     
  2. gonzo
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    gonzo Senior Member

    To figure out how much the boat sinks, first calculate the area of the waterline plane. You can take a few measurements for an approximate value. The weight of 1 cubic foot of water is 62 lb. If you divide the weight you are adding by 62 times the surface area (in square feet), it will give you feet of immersion. [Weight/62*Area in ft sq]
     
  3. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Wesley, your boat appears to have a nicely balanced waterline fore and aft, hence the waterplane coefficient (the ratio of the waterplane area to the area of the rectangle in the same length and breadth) will be fairly low (compared to say a boat with a wider transom, which might have a larger coefficient).
    I am hazarding a guess at around 0.6 for your waterplane area coefficient, which gives very approximately around 500 lbs per inch immersion for the first inch - the next inch will be a bit more, because the length and the beam are increasing a bit.
    Referring to the drawing of your boat here -
    SailboatData.com - ALBERG 30 Sailboat https://sailboatdata.com/sailboat/alberg-30
    I am thinking that even if you are going across the Atlantic, you don't really want to sink her much more than about 4" or 5" at the most beyond her load waterline as shown, so that would be about an extra ton at the most - including crew weight, stores, spares and extra equipment.
    Even a ton is quite a lot really - it is already 25% of her designed displacement.

    Re your weight estimates above, the Atomic 4 engine weight should be included in the displacement at the load draft, so you don't have to worry about that.
    Re carrying 80 gallons of fuel for this beast - there is no need for this much fuel unless you are looking for a thousand mile range under power alone - but you have sails. 15 gallons would be more normal, as mentioned in the Sailboat Data link - and a full fuel tank is probably included in that displacement, similarly a full water tank of 30 gallons.
    So most of that extra ton could be allocated to your crew weight, stores, spares and kit.
     
  4. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    According to the internet, no guarantees:
    • Stability Data
    • Lateral Center of Buoyancy: 16.1 Feet Aft of Bow
    • Max GZ (Righting Moment): 1.352 @ 60 Degrees
    • Prismatic Coeffient: 395
    • Sail Area/Displacement: 15.2
    • Beam/Length: .29
    • Ballast/Displacement: .37
    • Comfort Ratio: .32
    • Pounds per Inch Immersion: 676
    • Moment to trim 1 Degree: 775 lbs
    • Wetted Surface Area: 204 Square Feet
     
  5. wesley Sherman
    Joined: Jan 2020
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    Location: New York

    wesley Sherman Junior Member

    Thank you all so much, that was the information I was looking for, Answered all my question!
     
  6. wesley Sherman
    Joined: Jan 2020
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    Location: New York

    wesley Sherman Junior Member

    One last thing I am still trying to work out. A Lot was answered but still wondering how does one determine that is the probable max load to carry on this boat... I know it will carry allot but sink more but eventually won't a certain amount of weight be detrimental to the rigging and mast? When i gutted the boat I removed everything down to the hull and weighed the whole lot... as as i build and replace I weight all the materials I am installing, dont weight the fiberglass but as i go through the materials like Resin I record the weight.. I have the approx weight of the boat from stats, So working toward knowing what a borderline excessive weight might be.
    Thank you all !!
    Wesley
     
  7. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    I think that you will reach a stage when loading down the boat where the obvious effects of the extra weight on the stability (and hence concerns about seakeeping offshore) will be more important than any possible detrimental effects to the rigging and the mast.
    You have a relatively conservative rig, which no doubt has a fairly high factor of safety built in, so even if the boat ends up stiffer, and doesn't heel as much in a gust, she should still be able to cope with this ok.
    Re determining the probable max load - it is always a good idea to keep a record of the weights (approximately) going on and off the boat (as per what you are doing), as it is very easy to add weight, and more difficult to lose it (same as with people :) ) - but I think that generally you don't want to load her more than say 4" beyond her design waterline at the most. Rumars notes an immersion of approx 676 lbs / inch, so that is about 2,700 lbs of extra load, which should be more than enough for going across oceans, even if there are 2 of you on board.
     
  8. wesley Sherman
    Joined: Jan 2020
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    wesley Sherman Junior Member

    I agree with you Bajansailor.... From past reading of my fathers logs of our pacific cruising, we left in 1977 for Hawaii according to his log with approx 2350 he estimated in gear and the two of us.. so for one person you are very correct, I asked this question because i was thinking that somewhere there has to be some sort of dynamic effect of weight below. That weight below has to change the dynamics. of the above the deck rigging at some point would be affected do the weight its trying to push.
     

  9. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    If you are 'well loaded down' I don't think the dynamic effect of the weight below is going to have much effect on the dynamics of the rigging - rather, I think it will be more important to ensure that all that weight down below is securely stowed (ideally in lockers that can be properly secured) such that in the event of a knockdown (or worse, a capsize and subsequent righting, hopefully) it cannot go flying everywhere.
     
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